Process of purifying arylides of 2, 3-hydroxy-naphthoic acid



Patented Dec. 6, 1932 UNITED STATES PATENT OFFICE JOHN M. TINKER ANDLOUIS SPIEGLER, OF SOUTH MILWAUKEE, WISCONSIN, ASSIGNORS TO E. I. DUPONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A COR- PORATION OFDELAWARE PROCESS OF PURIFYING ARYLIDES 0F 2,3-HYDROXY-NAPHTHOIC ACID NoDrawing.

This invention relates to a process of purifying dyestuf'f intermediatesof the hydroxynaphthoic acid arylide series. It is an object of thisinvention to provide a simple, inexpensive and efficient method forpurifying arylides of 2,3-hydroxy-na-phthoic acid. Other and furtherimportant objects of this invention will appear as the descriptionproceeds.

The arylides of 2,3-hydroxy-naphthoic acid are generally prepared byreacting 2,3- hydroxy-naphthoic acid with the desired arylamines in aninert solvent in the presence of phosphorus trichloride or similardehydrating agents. In our copending application Ser. No. 575,48 l,filed of even date herewith is described a modification of said processwhereby the basic arylamine is replaced by a halogen acid salt thereof,such as the hydrochloride. According to other methods in the literature,the reaction is effected between 2,3-hydroxy-naphthoyl-chloride and thedesired arylamine.

In all the above cases the arylide body directly as obtained from thereaction mixture, that is, after removal of the solvent by evaporationin the presence of water, and washing the precipitate free ofphosphorous acid, is not obtained in pure state, but contains variousimpurities which affect the shade of the ultimate dyestufi. In order toobtain the pure shade characteristic of the particular arylide, it isnecessary to subject the said isolated product to a purificationtreatment.

Two methods of purification have generally been practiced in the art.According to one of these methods, the arylide of 2,3-hydroxy-naphthoicacid is dissolved in caustic soda solution, filtered, and the filtraterun into acid. According to the other method the arylide isrecrystallized from an organic solvent such as chlorobenzene,nitrobenzene, glacial acetic acid, etc.

Both of the above methods, however, suffer from serious defects whichreduce their efliciency. The first method requires dISSOlV- ing thearylide in a large volume of relatively concentrated caustic. Inalkaline medium of such high concentration the hydroxy- Applicationfiled November 16, 1931. Serial No. 575,485.

naphthoic arylide body is somewhat unstable and tends to decompose orpolymerize, with the result that although certain impurities are removedby the treatment, others are introduced in substitution, sometimes evenin greater quantity than the original impurities, especially if thealkaline solution of the arylide is permitted to stand for any length oftime. When the caustic solution is now poured into acid, theseimpurities precipitate together with the arylide body. The second methodrequires laborious and time consuming recrystallizations, andfurthermore, occasions great losses of the arylide body due to itspartial solubility in the mother liquors. Sometimes the quantitydissolved in the mother liquor can be recovered, but

this, of course, requires further laborious and time consumingoperations such as partial distillation and crystallization.

A third method has sometimes been practiced, namely boiling in weakmineral acid. This process, however, does not extract all theundesirable impurities, and is furthermore objectionable because itrequires special acid proof equipment.

We have now found that arylides of 2,3- hydroxy-naphthoic acid can bevery effectively rid of their attendant impurities by extraction withmild alkalis, which are not strong enough to dissolve appreciableamounts of the arylide body. As examples of such mild alkalis, aqueousammonia or sodium bicarbonate solutions may be mentioned. The simplicityand efficiency of this method will be at once apparent. In the firstplace the entire procedure requires but a single operation, namely, thetreatment of the arylide body with the mild alkali followed byfiltration and washing. No reprecipitation from acid or resolution andrecrystallization from an organic solvent are tary mill, either wet ordry and with or without a wetting agent. Where the dry method of millingis employed, the resultant intimate dry mixture is subsequentlysuspended in water and filtered. Any other means, however, formechanically mixing the aryli'de body and the weak alkaline solution maybe resorted to. When the milling operationhas been carried on for asufiicient length of-time toefiect intimate contact, the suspensionisfiltered, and the filter cake washed with water until free of alkali.

The resultant paste is directly suitable for use in the manufacture ofwater insoluble azo dyestufi's, in substance or on textile fiber.- Thecolors thus obtained are of high brilliance and exhibit the true shadeand bright ness characteristic of the particular aryl'ide andtheparticular diazo component selected.

,Without limiting our invention to any specific procedure, the followingexamples are given to illustrate our preferred mode of. carrying out thesame. Parts given are parts by weight.

V 7 Example 1 A wet filter cake, as obtained in the manufacture of2,3-hydroxy-naphthoic acid anilide after washing the product free ofacid, and containing 500 parts of 2,3-hyclroxynaphthoic acid anilide aremilled together with 70 parts of 20% aqueous ammonia in the presence ofsufiicient water to insure eflicient milling. When the anilide has beenreduced to sufiiciently fine size to insure intimate contact with theammonia, the mixture is filtered, and washed with warm water until freeof alkali. The product, when dried, melts at 247248 C. When used for theproduction of developed colors upon textile fibers it gives true andverybright shades.

acidified, a product precipitates,

milled'in a ball mill together with5l parts Example 2 506 parts of dry2-,3-hydroxy-na hthoic acid o-toluidide (M. P. 176186 are 500 parts ofdry 2,3-hydroxy-naphthoic acid-p-anisidide are milled in aball' milltogether with 50 parts of potassium bircarbomate and 0.1 part of thesodium salt of isopropyl-naphthalene-sulfonic acid. The object of thelatter is to aid in the subsequent wetting of the particles when themixture is suspended in water. When thus suspended, stirred, filteredand washed free of alkali, an extremely pure product is obtained,melting at 229.5230 C. This is practically 5 C. higher than the meltingpoint given in the at re, and u ly 6 high t an'the melting pointiOf thepeanisi;di de of commerce. i 7

Example 4 A wet cake containing 500 parts of the 2,5-dian1ethoxy-anilide of 2,3-hydroxy-naphthoic acid are milled togetherwith 100 parts of-s'odium acetate crystals, in the presence ofsufiicient water'to dissolve'the entire quantity of acetate and to forma free-milling sus pension of the arylide. The milling is continueduntil an intimate, fine, yet filterable suspension is obtained. Thelatter is filtered, and if washed free of alkali will give a prodnot ofconsiderabl greater purity thanthe initial material. li-Iowever, in viewof the weak alkali employed, the product is not at its highest puritydirectly from the first treatment. To increase the purity of this canproduct it is advantageous to subject the last filter cake to repeatedmilling with sodium acetate or any other weak alkali in the same manneras the-initial material was treated. Two or three treatments as aboveoutlined will give a productmelting at 1844853. C.

Example 5 V 586 parts of a 'dry powder analyzing 85.3 of2,3-hydroxy-nap'hthoic acid-B-naphthah ide are milled with 70 parts of20% aqueous ammonia as described in Example 1. The product, afterfiltering, washing and drying, contains 480 parts of pure2,3-hydroxynaphthoic acid-,R-naphthalide. When used as "couplingcomponent with diazo compounds it develops upon fabric bright colorsequalling in shade those obtainedby the use of Naphthol AS'SW ofcommerce. The in itial material when coupled to the same componentandtested against the same standard, produces very dull-shades,

In a similar manner other weakly alkaline salts may be used; forinstance, borax, disodium-hydrogen-phosphate, and the like;

It will be understood that many variations and modifications arepossible in our procedure without departing from the spirit. of thisinvention. For instance any of the abOve-menti0ned mild alkalis, or anyother mildly 'alkaline compounds may be used with any particular arylideof 2,3 hydrox-y-. naphthoic acid. The proportion of" alkaline agent toarylide body may be varied within wide limits; Excessive amounts are,however, to be avoided, in order'to'preventpos sibleloss of the arylidebody by solution.

Where the treatment is insuificient to give a product of desired purityin one extraction, it is preferable to repeat the operation rather thanincrease the proportion of alkaline substance. The desired degree ofpurity may be tested by the melting point of the final product, or byrepeating the extraction on a small sample and testing the alkalinemother liquors, by acidification, for extracted organic matter. Wettingagents, such as the sodium salt of isopropyl-naphthalene-sulfonic acid,the sodium salt of abietene-sulfonic acid, and the like, may be usedwith any of the alkaline agents or with any of the arylides for thepurpose of improving their Wetting during their treatment with Water.Dry compositions of the arylide body and an alkaline agent, with orWithout wetting agent, may be mad-e up for distribution in the trade, tobe extracted by the direct consumer by the mere steps of stirring inWater, filtering and washing. Numerous other variations and improvementswill readily suggest themselves to those skilled in the art.

e claim:

1. The process of purifying an arylide of 2,3-hydroxy-naphthoic acid,which comprises milling the same with an aqueous solution of a mildalkali which is not strong enough to dissolve appreciable quantities ofthe arylide body, filtering, and washing the filter cake untilsubstantially free of alkali.

2. The process of purifying an arylide of 2,8-hydroxy-naphthoic acid,which comprises of 2,3-hydroxy-naphthoic acid, the step which comprisesdry milling the same with a Water soluble, mildly alkaline compound, ofthe group comprising water soluble bicarbonates, acetates, borates andacid phosphates, and with a wetting agent.

8. As a composition of matter an intimate, dry mixture of'an arylide of2,8-hydroxynaphthoic acid and a Water-soluble, mildly alkaline compoundin finely divided form.

9. As a composition of matter an intimate, dry mixture of an arylide of2,3-hydroxynaphthoic acid and a water-soluble, mildly alkaline compoundin finely divided form selccted from the group consisting ofWatersoluble bicarbonates, acetates, borates and acid phosphates.

10. As a composition of matter an intimate, dry mixture of an arylide of2,3-hydroxynaphthoic acid, a wetting agent, and a watersoluble, mildlyalkaline compound, the entire mixture being in finely divided form.

11. As a composition of matter an inti mate, dry mixture of an arylideof 2,3-hydroxy-naphthoic acid, a wetting agent, and a water soluble,mildly alkaline compound, selected from the group consisting of watersoluble bicarbonates, acetates, borates and acid phosphates, the entiremixture being in finely divided form.

In testimony whereof we aifix our signatures.

JOHN M. TINKER. LOUIS SPIEGLER.

milling the same with an aqueous solution of a mild alkali selected fromthe group consisting of ammonia, alkali metal bicarbonates, acetates,acid phosphates, and borates, filtering, and washing the filter cakeuntil substantially free of alkali.

3. In the process of purifying an arylide of 2,3-hydroxy-naphthoic acid,the step which comprises forming an intimate mixture of the same with awater soluble, mildly alkaline compound selected from the groupconsisting of ammonia and water-soluble bicarbonates, acetates, boratesand acid phosphates.

4. In the process of purifying an arylide of 2,3-hydroxy-naphthoic acid,the step which comprises dry milling the same with a water soluble,mildly alkaline compound.

5. In the process of purifying an arylide of 2,8-hydroxy-naphthoic acid,the step which comprises dry milling'the same with a Water soluble,mildly alkaline compound, and a wetting agent.

6. In the process of purifying an arylide of 2,3 -hydroxy-naphthoicacid, the step which comprises dry milling the same with a watersoluble, mildly alkaline compound, of the group comprising water solublebicar bonates, acetates, borates and acid phosphates,

7. In the process of purifying an arylide

